Closing the geologic carbon cycle

• 成果类型: Article
• 署名作者: Derry, Louis A.
• 署名单位: Cornell University; Universite Paris Cite
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12060
• DOI: 10.1073/pnas.2409333121
• 发表日期: 2024-10-15
• 关键词: organic-carbon; isotope excursions; sedimentary carbon; co2; matter; ocean; burial; sulfur; preservation; consumption

摘要

Estimates of sedimentary organic carbon burial fluxes based on inventory and isotope mass balance methods have been divergent. A new calculation of the isotope mass balance using a revised assessment of the inputs to the ocean- atmosphere system resolves the apparent discrepancy. Inputs include weathering of carbonate and old kerogen, geogenic methane oxidation, and volcanic and metamorphic degassing. Volcanic and metamorphic degassing comprise approximate to 23% of the total C input. Inputs from isotopically light OCpetro and CH 4- geo drive the mean delta 13 C of the input to =-8.0 +/- 1.9 parts per thousand, notably lower than the commonly assumed volcanic degassing value. The isotope mass balance model yields a modern burial flux =15.9 +/- 6.6 Tmol y-1. The impact of the mid- Miocene Climatic Optimum isotope anomaly is an integrated excess deposition approximate to 4.3 x 106 Tmol between 18 and 11 Ma, which is both longer and larger than estimates for the total degassing by the Columbia River Basalt eruptions, implying a complex carbon system response to large eruptive events. Monte Carlo evaluation finds that late Cenozoic net growth of the carbonate reservoir is very likely while net growth of the C org reservoir is less certain but more likely than not. At present, subduction does not appear to keep up with net sedimentation and the overall masses of sedimentary carbonate and organic carbon are likely increasing. Growth in the sedimentary C org reservoir implies oxidation of the surface environment and likely increases in atmospheric pO2.